1. Technical Field
The present invention generally pertains to a system for characterizing the energy losses within an internal combustion engine. More particularly, but without restriction to the particular embodiment and/or use which is shown and described for purposes of illustration, the present invention relates to an engine friction characterization system used in conjunction with a torque based idle control system.
2. Discussion
The internal combustion engine of today's motor vehicle is a complicated, dynamically changing machine. In order to maximize performance and increase component durability, it is desirable to have the capability of controlling an engine to produce a specific output torque. To accomplish this task, an accurate estimate of the energy loss due to friction must be calculated. Characterizing friction within an internal combustion engine requires a very elaborate set of models and equations. However, current engine control processors cannot accommodate this level of complexity. As a result, a simplified approach needs to be developed that not only reduces the amount of processor time required to calculate the frictional losses, but one that also retains much of the original accuracy.
Conventional engine control systems have either completely ignored engine frictional losses or have attempted to incorporate a simple constant percentage loss as part of the model. While these methods have provided some benefit in the past, improvements may be made. Specifically, by using the simplified approach described herein, a characterization of the engine friction loss may be made. Using this data, the engine control unit may accurately estimate the engine's true output torque at any time. A torque management algorithm may be implemented to assure that only the proper level of torque enters the driveline components. Accordingly, it is possible to increase component performance and durability while reducing computer processing overhead. In addition, an accurate estimate of engine output torque is valuable information when utilized by other control systems within the vehicle such as the traction control system and the transmission control system.